Abstract : The report summarizes research on the following topics: energy fluctuations and rotons in liquid helium; Landau's theory of liquid helium; the motion of a sphere in a perfect fluid; the fundamental laws of thermodynamics and statistical mechanics; interatomic forces in and thermodynamic properties of solid argon; melting phenomena in simple solids; thermodynamics and statistical mechanics of critical lines and critical points, with applications to 3He-4He mixtures, binary liquid systems, and pure substances; experimental work on coexistence curves in binary liquid systems, and experimental and theoretical work on the effect of impurities; experimental equipment for temperature control. A bibliography and list of coworkers are included. (Modified author abstract)